Analysis and Design of Ultra Thin Electromagnetic Absorbers Comprising Resistively Loaded High Impedance Surfaces

TLDR

The paper designs ultra‑thin electromagnetic absorbers using high‑impedance surfaces with lossy frequency‑selective surfaces and employs an equivalent‑circuit model to identify the optimal element for wideband absorption. The absorbers are realized by printing resistive inks on the FSS pattern to introduce losses, and a circuit model is used to analyze how surface resistance and substrate properties affect input impedance and to explain the narrowband and wideband behavior. The fabricated absorbers achieve very wideband absorption in a reduced thickness, with the optimal surface resistance depending on substrate thickness, permittivity, and FSS shape, and experimental tests confirm the predicted performance.

Abstract

High-Impedance Surfaces (HIS) comprising lossy Frequency Selective Surfaces (FSS) are employed to design thin electromagnetic absorbers. The structure, despite its typical resonant behavior, is able to perform a very wideband absorption in a reduced thickness. Losses in the frequency selective surface are introduced by printing the periodic pattern through resistive inks and hence avoiding the typical soldering of a large number of lumped resistors. The effect of the surface resistance of the FSS and dielectric substrate characteristics on the input impedance of the absorber is discussed by means of a circuital model. It is shown that the optimum value of surface resistance is affected both by substrate parameters (thickness and permittivity) and by FSS element shape. The equivalent circuit model is then used to introduce the working principles of the narrowband and the wideband absorbing structure and to derive the best-suited element for wideband absorption. Finally, the experimental validation of the presented structures is presented.